Delivery system for medical devices

ABSTRACT

The invention is directed a delivery system for implantation a self-expanding medical device in a body which includes a control handle and a catheter portion. The catheter portion includes an outer restraining member which covers the collapsed, medical device, an inner catheter member having a distal end including a region upon which the medical device is mounted, and an outer sheath which is removably attached to the control handle. The outer sheath creates a conduit for the catheter portion to prevent the inner catheter member from moving axially when the outer restraining member is retracted. The control handle has a rotatable thumbwheel to actuate a retraction mechanism attached to the proximal end of the outer restraining member which moves the restraining member in a proximal direction to deploy the medical device.

BACKGROUND OF THE INVENTION

The present invention relates generally to delivery systems fordelivering and deploying medical devices, such as stents, which areadapted to be implanted into a patient's body, such as a blood vesseland, more particularly, to a delivery system for more accuratelydeploying a self-expanding medical device into an area of treatment.

Stents are generally cylindrically shaped devices which function to holdopen and sometimes expand a segment of a blood vessel or other arteriallumen, such as coronary artery. Stents are usually delivered in acompressed condition to the target site and then deployed at thatlocation into an expanded condition to support the vessel and helpmaintain it in an open position. They are particularly suitable for useto support and hold back a dissected arterial lining which can occludethe fluid passageway there through. Stents are particularly useful inthe treatment and repair of blood vessels after a stenosis has beencompressed by percutaneous transluminal coronary angioplasty (PTCA),percutaneous transluminal angioplasty (PTA), or removed by atherectomyor other means, to help improve the results of the procedure and reducethe possibility of restenosis. Stents, or stent-like devices, are oftenused as the support and mounting structure for implantable vasculargrafts which can be used to create an artificial conduit to bypass thediseased portion of the vasculature, such as an abdominal aorticaneurism.

A variety of devices are known in the art for use as stents and haveincluded coiled wires in a variety of patterns that are expanded afterbeing placed intraluminally on a balloon catheter; helically woundcoiled springs manufactured from an expandable heat sensitive metal; andself-expanding stents inserted into a compressed state for deploymentinto a body lumen. One of the difficulties encountered in using priorart stents involve maintaining the radial rigidity needed to hold open abody lumen while at the same time maintaining the longitudinalflexibility of the stent to facilitate its delivery and accommodate theoften tortuous path of the body lumen.

Prior art stents typically fall into two general categories ofconstruction. The first type of stent is expandable upon application ofa controlled force, often through the inflation of the balloon portionof a dilatation catheter which, upon inflation of the balloon or otherexpansion means, expands the compressed stent to a larger diameter to beleft in place within the artery at the target site. The second type ofstent is a self-expanding stent formed from shape memory metals orsuperelastic nickel-titanium (NiTi) alloys, which will automaticallyexpand from a compressed state when the stent is advanced out of thedistal end of the delivery, or when a restraining sheath which holds thecompressed stent in its delivery position is retracted to expose thestent.

Some prior art stent delivery systems for delivery and implantingself-expanding stents include an member lumen upon which the compressedor collapsed stent is mounted and an outer restraining sheath which isinitially placed over the compressed stent prior to deployment. When thestent is to be deployed in the body vessel, the outer sheath is moved inrelation to the inner member to “uncover” the compressed stent, allowingthe stent to move to its expanded condition. Some delivery systemsutilize a “push-pull” type technique in which the outer sheath isretracted while the inner member is pushed forward. Another commondelivery system utilizes a simple pull-back delivery system in which theself-expanding stent is maintained in its compressed position by anouter sheath. Once the mounted stent has been moved at the desiredtreatment location, the outer sheath is pulled back via a deploymenthandle located at a remote position outside of the patient, whichuncovers the stent to allow it to self-expand within the patient. Stillother delivery systems use an actuating wire attached to the outersheath. When the actuating wire is pulled to retract the outer sheathand deploy the stent, the inner member must remain stationary,preventing the stent from moving axially within the body vessel.

However, problems have been associated with such prior art deliverysystems. For example, systems which rely on a “push-pull design” or“push-back design” can experience unwanted movement of the collapsedstent within the body vessel when the inner member is pushed forwardwhich can lead to inaccurate stent positioning. Systems which utilize a“pull back” system or an actuating wire design will tend to move tofollow the radius of curvature when placed in curved anatomy of thepatient. As the outer sheath member is actuated, tension in the deliverysystem can cause the system to straighten. As the system straightens,the position of the stent changes because the length of the catheter nolonger conforms to the curvature of the anatomy. This change of thegeometry of the system within the anatomy can lead to inaccurate stentpositioning.

Delivery systems which utilize the “pull-back” type technique usuallyrequire removal of “slack” developed between the outer sheath and theinner catheter member upon which the stent is mounted. Generally, theexposed catheter, i.e. the portion of the outer member which remainsoutside of the patient, must usually be kept straight or relativelystraight during deployment. Failure to do so may result in deploying thestent beyond the target area and can cause the stent to bunch up. Thisphenomenon occurs because the inner catheter member tends to moveforward when the outer sheath is retracted. The reason why this happensis because the inner catheter member and outer catheter member aretypically the same length prior to stent deployment. The length of theexposed catheter, again, the portion of the outer catheter which extendsbetween the deployment handle and the insertion point in the patient,however, is usually fixed. When the outer sheath is retracted proximallyinto the deployment handle during deployment, the length of the exposedouter sheath tends to shorten. The inner catheter member, however,remains the same length as it is held fixed in the deployment handle.However, the outer sheath tends to shorten during deployment, thuschanging the shape of the exposed portion of the catheter. This shapechange occurs because the outer sheath wants to straighten out once it'sbeing retracted. Since the inner catheter member is fixed proximallywithin the deployment handle, it will move distally as the outer sheathis retracted. As a result, the movement of the inner catheter membercaused by the retraction of the outer sheath can cause the stent todeploy prematurely and at a location beyond the targeted site. As aresult, less than accurate deployment of the stent can occur.

This problem usually does not exist when the delivery system is keptstraight during deployment as the outer sheath is allowed to slideproximally relative to the inner catheter member. However, if thedelivery system is not kept straight during deployment, then the innercatheter member has this tendency to move distally during deployment.This change in the shape of the exposed catheter forces the innercatheter member to change shape as well in order for the inner cathetermember to maintain the same length as the outer sheath. Since the innercatheter member is fixed within the deployment handle, it can only movedistally. Consequently, the inner catheter member moves distally alongwith the mounted stent, causing the stent to be deployed beyond thetargeted site in the patient's anatomy.

The above-described stent delivery systems also can be somewhatdifficult to operate with just one hand, unless a mechanical advantagesystem (such as a gear mechanism) is utilized. Often, deployment withone hand is desirable since it allows the physician to use his/her otherhand to support a guiding catheter which may be utilized during theprocedure. The above-described stent delivery systems should not besusceptible to any axial movement of the catheters during stentdeployment. Even a slight axial movement of the catheter assembly duringdeployment can cause some inaccurate placement of the stent in the bodylumen. Some stent delivery systems employ a control handle whichutilizes a pistol grip actuator that requires the physician torepeatedly pull back a trigger mechanism to cause the outer sheath toretract. In doing so, the physician usually creates a backwards force onthe delivery system which also can cause the catheter portion of thedelivery system to move within the patient's vasculature, resulting inless than accurate placement of the stent within the patient. Also, someof these stent delivery systems have a limited range of retraction ofthe outer sheath which can limit the use of the delivery system tosmaller medical devices which require only a small amount of retractionin order to expand the device. Larger medical devices, such asvasculature grafts, cannot be deployed because the control handle of thesystem cannot retract the outer sheath a sufficient length in order toexpose the entire graft.

Thus, there is a need for a delivery system for delivering and deployinga self-expanding medical device, such a stent, which prevents the axialmovement of the inner catheter member relative to the outer sheath toprevent the inner catheter member from moving forward during deployment.Such a delivery system also should also compensate for any slack thatmay be present in the delivery system and should prevent the innercatheter member from moving forward within the patient's vasculature asthe outer restraining sheath is being retracted from the self-expandingmedical device. Such a delivery system would be beneficial if it allowedthe physician to actuate the system with only one hand, thus allowingthe physician to use his/her other hand during the procedure. Thepresent invention disclosed herein satisfies these and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to a delivery system for deliveringand more accurately deploying a medical device, such as a stent, to thetarget site in a body lumen. The delivery system in accordance with thepresent invention incorporates unique features which facilitates minimalmovement during device deployment, accurate placement, and single-handedsystem operation. While the delivery system can be used to deploy anyself-expanding stent, it also can be used to deploy other self-expandingmedical devices, including medical devices which are not self-expandingas well.

In one aspect of the present invention, the delivery system include acontrol handle and a catheter portion which is designed for advancementto a target area in a patient's body lumen over a deployed guide wireusing “over the wire” techniques known in the art. The catheter portionincludes an inner catheter member having a proximal portion attachedwithin the control handle and a distal portion upon which the medicaldevice is mounted in a collapsed position. An outer restraining memberextends over the inner catheter member in a coaxial arrangement. Theouter restraining member holds the medical device in the collapsedposition until the device is to be deployed. If the medical device isnot self-expanding, the outer restraining member does not necessarilyrestrain the device, but provides a protective cover for the device. Theouter restraining member is retractable to release the medical device bya retraction mechanism housed in the control handle. The control handleincludes a rotatable thumbwheel which is easily moveable to provide amanual mechanism for retracting the restraining sheath. The controlhandle immobilizes the inner catheter member, preventing it from movingrelative to the outer restraining member during deployment. The controlhandle allows the delivery system to be operated by just one hand,freeing the physician's other hand for other purposes, such asstabilizing the guiding catheter during deployment of the medicaldevice.

In one aspect of the present invention, the catheter portion includes anouter sheath which is utilized to stiffen the catheter portion of thedelivery system so that the inner catheter member will not change shapeoutside the body when the outer restraining member is retracted todeploy the medical device. The outer sheath extends at least partiallyover the length of the outer restraining member in a coaxialrelationship in order to create a conduit between the control handle andthe point of insertion into the patient. This outer sheath helps toreduce frictional forces which may be created with the medical devicethat is inserted into the patient to obtain entry for the catheterportion, such as a rotating hemostatic valve (RHV), or other similardevice, and helps to prevent the inner catheter member from movingdistally as the outer restraining sheath is being retracted via thecontrol handle.

In another aspect of the present invention, the outer sheath is attachedto a strain relief member which is threadingly engaged with the controlhandle. In this particular aspect of the invention, the proximal end ofthe strain relief has a channel formed in it which is designed toreceive a tab-like projection formed in a recess of the control housingin order to allow the strain relief member to be threaded onto thecontrol handle. Depending upon physician preference, the outer sheathcan either remain or be removed from the control handle during use.

In another aspect of the present invention, the retraction mechanism ofthe control handle allows the outer restraining member to be retractedin a proximal direction only and includes a stop mechanism whichprevents the retraction mechanism from prematurely deploying. Thecontrol handle allows the physician to actuate the retraction mechanismusing a simple thumb motion on the thumbwheel which helps to preventunwanted forces from acting on the control handle which can typically bedeveloped when a pistol-like actuated control handle is utilized. As aresult, a more accurate placement of the medical device may be achieved.

The inner catheter member has a guide wire lumen which extends from thedistal end of the inner catheter member to the proximal end to allow aguide wire to be used to advance the catheter portion to the target areain the body lumen in an “over the wire” technique. In this regard, thecatheter/medical device can be introduced within the patient'svasculature in a conventional Seldinger technique through a guidingcatheter. The distal end of the inner catheter member includes a soft,low profile tip assembly with a radiopaque marker.

These and other advantages of the present invention become apparent fromthe following detailed description and the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a control handle which forms partof the delivery system of the present invention.

FIG. 2 is an elevational view, partially in section, showing a schematicrepresentation of the catheter portion of the delivery system whichattaches to the control handle.

FIG. 3 is a perspective view of a delivery system showing the flatteningof the arc during deployment in silhouette.

FIG. 4 is a cross sectional view of the control handle of FIG. 1.

FIG. 5 is an enlarged cross-sectional view of the retraction mechanismof the control handle of FIG. 4.

FIG. 6 is a cross-sectional view of the control handle of FIG. 4 inwhich the rack and pinion portion of the control handle has beenpartially retracted.

FIG. 7 is a perspective view showing the proximal end of the strainrelief portion of the catheter system which is attached to the outersheath utilized in conjunction with the present delivery system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a delivery system for delivering anddeploying a medical device into a target site in a patient's body, suchas a body lumen. For sake of illustration, the following exemplaryembodiments are directed to a delivery system for delivering anddeploying a self-expanding stent, although it is understood that thepresent invention is applicable to other medical devices which areimplantable in a body lumen as well as other parts of the body.Additionally, the medical device can be either a self-expanding deviceor a non self-expanding device.

Referring now to FIGS. 1 and 2, in one particular embodiment of thepresent invention, the delivery system 10 incorporating features of thepresent invention includes a control handle 12 and a catheter portion14. As can best be seen in FIG. 1, the control handle includes a handportion 16 which allows the physician to hold the control handleutilizing one hand. The control handle 12 also includes a rotatablethumbwheel 18 which allows the physician to retract the restrainingsheath utilized to maintain the self-expanding medical device in itscollapsed, delivery position near the distal end of the catheter portion14 of the system. The hand portion 16 can be easily grasped by thephysician and the thumbwheel 18 can be easily rotated by the physicianto actuate the mechanism which pulls back the restraining sheath toexpose the self-expanding stent to achieve deployment of the devicewithin the patient. A lock mechanism 20 is utilized to maintain thecatheter portion 14 of the device in a securely locked condition untilthe physician is ready to manipulate the thumbwheel 18 to deploy themedical device. The design of the control handle allows the physician tohold the hand portion 16 in either his/her right or left hand and easilymanipulate the thumbwheel 18. Alternatively, the physician can grasp theportion of the control handle distal to the thumbwheel 18 if desired,and still be capable of easily rotating the thumbwheel 18 in order toretract the restraining sheath. This sleek design of the control handleallows added versatility when handling and deploying the delivery systemmade in accordance with the present invention.

Referring now specifically to FIG. 2, the catheter portion 14 is shownschematically as including an inner catheter member 22 which is adaptedto carry the medical device, such as a self-expanding stent 24, near thedistal end of the inner catheter member 22. An outer restraining memberextends generally coaxially over the inner catheter member 22 and isdesigned to maintain the stent 24 in its collapsed deliveryconfiguration until the stent is to be deployed by the physician. Thisouter restraining member 26 can be retracted via the control handle 12in accordance with the present invention. A third catheter member formsthe outermost catheter portion 14 of the system and is shown as an outersheath 28 which is removably attached to the control handle 12. In thisregard, the outer sheath 28 is coaxially disposed over the outerrestraining member 26 and can be removably attached to the controlhandle 12 or attached to a strain relief 30 which is removably attachedto a nose cone 32 forming part of the control handle 12. Further detailson the construction of the removable strain relief 30 and its attachmentto the nose cone 32 are described in greater detail below.

The outer sheath 28 is utilized in order to stiffen the catheter portionof the delivery system so that the arc of the inner catheter member 22will not change shape outside the body when the outer restraining member26 is pulled back to deploy the stent. In this regard, the innercatheter member 22 can be maintained in a stationary position relativeto the control handle 12 and the outer restraining member 26 so that theinner catheter member 22 will not move distally once retraction of theouter restraining member 22 commences.

Referring specifically now to FIG. 3, the problem that exists when adelivery system does not utilize an outer sheath 28, such as the onemade in accordance with the present invention, is described in greaterdetail. FIG. 3 shows the delivery system as it extends outside of thepatient 34 (schematically represented in FIG. 3). A rotating hemostaticvalve 36 is shown schematically inserted within the patient 34. In FIG.3, the delivery system is shown without the outer sheath 28 connected tothe control handle 12 and merely represents an outer restraining member26 coaxially disposed over the inner catheter member 22. When thedelivery system is maintained at a curvature with respect to the entrypoint, i.e. at the rotating hemostatic valve 36, the inner cathetermember has a tendency to move distally during the retraction of theouter restraining member. FIG. 3 shows the presence of a curvature inthe exposed portion of the catheter portion prior to deployment. In thisstate, the lengths of the inner and outer members are substantially thesame. However, the outer restraining member tends to shorten duringdeployment, thus changing the shape of the exposed portion of thecatheter. This shape change occurs because the outer restraining memberwants to straighten out once it's being retracted. This change in theshape of the outer restraining member is shown in silhouette 38 in FIG.3. Since the inner catheter member is fixed proximally within thecontrol handle, it will move distally as the outer restraining member isretracted. As a result, the movement of the inner catheter member causedby the retraction of the outer restraining member can cause the stent todeploy prematurely and at a location beyond the targeted site. As aresult, less than accurate deployment of the stent can occur.

The outer sheath 28 is designed to attach to the point of entry in thepatient, for example the rotating hemostatic valve 36 located at theinsertion opening in the patient's vasculature, to avoid the prematuredeployment of the stent since this outer sheath 28 creates a conduitthat allows the outer restraining member 26 of the catheter portion 14to move without excessive friction. The outer diameter of the outersheath 28 can remain compatible to a specified sheath sizing or it caninclude a necked-down distal region 29 in which the inner and outerdiameters of the outer sheath 28 is less than the remainder of the outersheath. This necked-down region 29 helps to reduce the possibility ofblood loss through the annular space formed between outer sheath and theouter restraining member. The outer sheath 28 ensures accuratedeployment without the need to remove slack from the exposed catheterportion, i.e. the portion of the catheter which extends between therotating hemostatic valve and the control handle. As a result, aphysician utilizing the delivery system of the present invention may notbe required to keep the exposed catheter portion straight orsubstantially straight in order to achieve accurate placement of thestent.

Referring again specifically to FIG. 2, the various components making upthe catheter portion 14 of the delivery system 10 are described ingreater detail herein. The inner catheter member 22 extends from thecontrol handle 12 to a distal portion which includes a region formounting the self-expanding stent 24. In one particular embodiment ofthe present invention, the inner catheter member 22 is a compositestructure formed of two different type of tubing, each tubing having aspecific function. FIG. 2 shows the inner catheter member 22 including aproximal portion 40, made from a hypotube, which extends within thecontrol handle 12 as is shown in FIGS. 4-6. The distal portion 41 of theinner catheter member which is attached distal to the proximal portion40 and can be made from polymide material which is braided withstainless steel which serves to provide a strong, but flexible, catheterportion in order to provide good trackability and pushability over aguide wire (not shown). The application of tensile force to the shaft ofthe outer restraining member 26 and outer sheath 28 during stentdeployment can create an equal and opposite compressive force on theinner catheter member 22. For the outer restraining member 26 to retract(via the movement of the control handle 12) without causing the rest ofthe catheter portion 14 to buckle, the inner catheter member 22 mustpossess sufficient column strength to prevent buckling or deformation.Otherwise, buckling or deformation to the inner catheter member 22 cancause the distal end of the catheter portion 14 to move within theartery, causing inaccurate deployment of the stent. Therefore, thetubing used to form the distal portion 41 of the inner catheter member22 should be fabricated from a tubular element which possessessufficient rigidity to prevent unwanted buckling or deformation, yet isflexible enough to track along the torturous anatomy to the target site.

Alternative tubing includes a more flexible material such aspolyethereketone (PEEK) or similar material which possess excellentcompressive strength, yet is reasonably flexible. The proximal portion40 can be made from hypotube which provides maximum strength, but isfairly rigid. However, this is not a concern since this proximal portion40 of the inner catheter member 22 remains relatively straight withinthe control handle 12. The distal portion of the inner catheter member22 must exit the guiding catheter and track through the torturousanatomy to reach the target site. Therefore, this portion must possesssufficient compressive strength, yet be fairly flexible.

As mentioned above, the inner catheter member 22 further includes thedistal portion which has the stent 24 mounted thereto. The distal end ofthe inner catheter member 22 includes a stent holder 43 which is formedbetween a proximal abutting shoulder 42 and a distal abutting shoulder44. These shoulders create an area for mounting the self-expanding stent24 in its collapsed position. These shoulders 42 and 44 also help tomaintain the stent on the stent holder of the inner catheter member 22as the outer restraining member 26 is retracted. The proximal shoulder42 provides an abutting surface which contacts the end of the stent inthe event frictional forces act on the stent as the outer restrainingmember 26 is being retracted. A distal marker 46 made from a highlyradiopaque material, such as tantalum or a platinum iridium alloy (Pt/IR90%/10%), provides a visual reference point for the physician whenutilizing fluoroscope or other imaging equipment. The shoulder 42 alsocan be made from a highly radiopaque material to serve as a visualmarker as well. A soft tip 48 is attached to the inner catheter member22 in order to create an atraumatic tip to help prevent snow plowing ofthe catheter portion as it is being delivered in an over-the-wirefashion along a guide wire. For example, the soft tip 48 can be madefrom a polymeric material such as polyether-block co-polyamide polymersold under the trademark PEBAX 25b-barium sulfate, a soft material whichincludes a radiopaque element that provides an additional visualizationpoint for the physician during fluoroscopy.

A guide wire lumen 50 extends along the entire length of the innercatheter member 22 and can be made from a tri-layer of materials such asPEBAX 72D, primacore and HDPE. The guide wire lumen 50 extends throughthe soft tip 48 and is attached to a luer fitting 52 mounted within arecess formed in the control handle 12. The luer fitting 52 permits thecontrol handle to be attached to syringes used to flush the system andalso provides an opening for the guide wire. The luer fitting 52 isattached at the proximal end of the hypotube and fits within the recessformed in the control handle to prevent the inner catheter member 22from moving relative to the outer restraining member 26 during stentdeployment. The luer fitting 52 can be attached to the hypotube 40 bygluing the fitting and hypotube together using a suitable adhesive. Itshould be appreciated that the mounting of the inner catheter member 22to the control handle 12 can be achieved in any number of ways withoutdeparting from the spirit and scope of the present invention.

This guide wire lumen 50 can be made from other materials which providea low friction interface between the delivery catheter and the guidewire which is used in the procedure to advance the catheter portion tothe target site using over-the-wire techniques that are well known inthe art. For example, the guide wire lumen can be made from tubing whichis compatible with a 0.014 inch guide wire for an over-the-wireconfiguration.

The guide wire lumen 50 extends from the distal end of the innercatheter member 22 to the proximal end to allow a guide wire to be usedto advance the catheter portion 14 (with mounted stent 24) to the targetarea in the body lumen in an “over the wire” technique. In this regard,the catheter portion 14 can be introduced within the patient'svasculature using, for example, a conventional Seldinger techniquethrough a guiding catheter.

The outer surface of the inner catheter member can be coated with asilicone lubricant such as Microgilde manufactured by AdvancedCardiovascular Systems, Inc., Santa Clara, Calif., to further reduce theamount of frictional buildup between the outer restraining member andinner catheter member.

In one embodiment of the present invention, the outer restraining member26 is a composite structure formed from three different sized tubingmaterials, each tubing material having a specific function. The outerrestraining member 26 is shown including a proximal portion 54 whichextends within the control handle 12 and is attached to the mechanismwhich produces the retraction force needed to retract the outerrestraining member from the stent. This proximal portion 54 of the outerrestraining member 26 is designed to move axially (along thelongitudinal axis of the control handle). This proximal portion 54 ofthe outer member can be made from a material such as a polymide. Theouter restraining member 26 also includes a mid-portion 56 which canalso be made from a material such as a polymide or other similarmaterial which provide a low profile, yet is strong enough to developthe pushability needed as the delivery system is moved along the guidewire in an over-the-wire delivery. This mid-portion 56 can be made withtubing having a different wall thickness than the proximal portion 54.The outer restraining member 26 also includes a distal portion 58 whichhas a larger inner diameter than the tubing forming the mid-portion 56in order to obtain the necessary diameter to maintain the collapsedself-expanding stent 24 in position on the system. This portion of theouter restraining member 26 is designed to hold the stent 24 in itscompressed or collapsed state and is retracted by actuating thethumbwheel 18 of the control handle 12 which proximally moves therestraining member while maintaining the inner catheter member 22stationary during stent deployment. The distal portion 58 can be madefrom a material such as polymide or other suitable materials which willprovide the necessary restraining force needed to keep theself-expanding stent in place. Since it is usually desired to have a lowprofile at this distal location of the catheter, a tubing having athinner wall thickness can be utilized.

Alternative material for forming the outer restraining member 26includes material such as cross-linked HDPE. Alternative materials forthe distal portion 58 include materials such as polyolefin which can bebonded to the mid-portion 56 of the outer restraining member 26. Amaterial such as polyolefin is used since it has sufficient strength tohold the compressed stent and has relatively low frictionalcharacteristics to minimize any friction between the stent and thetubing. Friction can be further reduced by applying a coat of siliconelubricant, such as Microgilde, to the inside surface of the distalportion 58 before the stent is loaded onto the stent holder.

The outer sheath 28 extends along a portion of the length of the outerrestraining member 26 as is necessary to create the conduit for thelength of the catheter which remains outside the patient. The length ofthis outer sheath 28 can be varied depending upon the size of themedical device mounted on the distal end of the inner catheter member22. In this regard, the length of the outer sheath 28 generally can beas long as, or longer than, the guide catheter (not shown) utilized whenthe delivery system is placed in the patient's vasculature.

In one aspect of the invention, the outer sheath 28 includes theneck-down region 29 in which the inner diameter of the outer sheath 28is comparable to the outer diameter of the mid-portion 56 of the outerrestraining member 26. In this fashion, a fairly tight fit extendsbetween these two catheter portions in order to minimize blood lossbetween these catheter portions. Since the distal portion 58 has alarger diameter than the tubing forming the mid-portion 56, the distalend of the outer sheath 28 should generally terminate a sufficientdistance to allow the outer restraining member 26 to be fully retractedby the control handle 12, while preventing the larger diameter distalportion 58 from abutting the distal end of the outer sheath 28. In thisregard, for example, if a 40 mm stent is mounted on the inner cathetermember 22, then the length of the retraction needed to properly releasethe device would require that the distal end of the outer sheath 28 beat least 40 mm away from the transition portion where the mid-portion 56translates to the distal portion 58 to allow the outer restrainingmember 26 to retract properly. If a longer length medical device ismounted on the inner catheter member 22 then the overall length of theouter sheath 28, of course, should be adjusted. It is also possible forthe inner diameter of the outer sheath 28 to be at least as large as theouter diameter of the distal portion 58 of the outer restraining sheath26 to allow proper retraction of the outer restraining sheath 26.

The outer sheath 28 can be made from materials such as polymide andother suitable materials. Other materials include polyetheretherketone(PEEK) and polyether-block co-polyamide polymer sold under the trademarkpurple PEBAX SA2032476. The strain relief 30 which is attached to theproximal end of the outer sheath can be made from a material such asPebex 70D. As will be described in greater detail below, the strainrelief 30 includes a proximal end 60 which can be threaded into the nosecone 32 of the control handle 12 to allow the physician to remove theouter sheath 28, if not needed.

Referring now to FIG. 7, the proximal end 60 of the strain relief 30 isshown in greater detail. As can be seen from this figure, the proximalend 60 includes a continuous channel 62 which creates a maze-like threadthat allows the strain relief 30 to be removably attached to the controlhandle 12. This maze-like channel threads into the nose cone 32 andallows the outer sheath 28 to be connected or detached based uponphysician preference. Referring specifically now to FIGS. 4 and 6, thechannel 62 of the proximal end 60 is adapted to be threaded along atab-like projection 64 which extends into the recess of nose cone 32 ofthe control handle 12. This tab-like projection 64 can be sized orshaped to fit within the channel 62. A projection stop element 66, whichextends within this channel 62, acts like a detent once the proximal end60 of the strain relief 32 has been threaded into the nose cone. Thisprojecting stop 66 prevents the strain relief from being moved from thenose cone until the physician desires to remove the outer sheath fromthe control handle. In this manner, the area 68 adjacent to theprojecting stop 66 is designed to contain the tab-like projection 64until the physician is ready to remove the outer sheath. The physiciancan remove the outer sheath 28 by simply twisting the strain relief 32to allow the tab-like projection 64 to move past the projecting stopelement 66 and then be moved along the channel 62 until the projection64 disengages from the channel. It should be appreciated that othercoupling means could be formed or attached to the control handle,besides a tab-like projection 64, to receive the channel 62.Additionally, the outer sheath 28 does not have to be attached to thestrain relief 30, but can be removably attached to the control handleitself. In this regard, the proximal end of the outer sheath can have asimilar channel formed therein as is shown in FIG. 7.

The control handle 12 of the present delivery system 10 will bedescribed in greater detail herein. Referring now specifically to FIGS.4-6, a cross sectional view of the actuating mechanism housed within thecontrol handle 12 is shown. The thumbwheel 18 of the control handle 12is connected to the actuating mechanism which is adapted to retract theouter restraining member 26 relative to the inner catheter member 22 toallow the distal portion 58 of the outer restraining member to retractfrom the stent and cause it to self-expand into the target area. Theactuator mechanism includes a slideable gear rack 70 which is disposedwithin a channel 72 formed along the length of the control handle 12.The slideable gear rack 70 is in turn attached to a spur gear 74 whichengages the gears 76 on the gear rack 70. The thumbwheel 18 is connecteddirectly to an actuating gear 78 which rotates as the thumbwheel isrotated by the physician. In this regard, once the thumbwheel 18 isrotated, the spur gear 74 is rotated by the actuating gear 78 causingthe gear rack 70 to move proximally within the channel 72 formed in thecontrol handle. FIG. 6 depicts the gear rack 70 in a position in whichthe gear rack 70 has been somewhat retracted through the rotation of thethumbwheel 18. Since the delivery system 10 can be used with just onehand, the physician's other hand is free to perform other tasks, such asstabilizing the guiding catheter used during the procedure. Bystabilizing the guiding catheter as well, enhanced accuracy in deployingthe stent can be obtained

A lock mechanism 20, as shown in FIGS. 4 and 5, extends into the controlhandle to prevent the gear rack 70 from moving until the physician isready to deploy the stent. In this regard, the lock mechanism 20includes a locking arm 80 which is designed to abut against a stopelement 82 formed or attacked to the gear rack 70. As can be seen inFIG. 5, the locking arm 80 is shown in an abutting relationship with thestop element 82 to prevent the gear rack 70 from moving proximally inorder to prevent retraction of the outer restraining member 26. The lockmechanism 20 includes a cam-like spring 84 designed to slide along asurface 86 formed into the body of the control handle 12. When the lockmechanism 20 is moved proximally by the physician, the locking arm 80moves upward and away from the stop element 82 to permit the stopelement 82 to move past it. It should be appreciated that this is justone mechanism which can be utilized to prevent unwanted retraction ofthe outer restraining member 26.

A spring 88 is mounted on a tab or protrusion 90 formed on the body ofthe control handle 12. This spring 88 is designed to contact the distalsurface 91 of the gears 76 forming the gear rack 70 to prevent the gearrack 70 from moving distally at any time. As a result, the controlhandle 12 of the present invention is capable of moving the outerrestraining member in one direction, namely proximally. In this regard,the spring 88 allows the control handle to store energy and prevents thephysician from losing energy during deployment. The spring 88accomplishes this by creating an abutting edge 89 which contacts thedistal surface 91 of the gears 76, as is shown in FIG. 5, preventing thegears 76 from moving distally, but allowing movement of the gear rack 70in a proximal direction. The spring 88 could alternatively be placed inan abutting arrangement with one of the gears of the other moveablecomponents forming the retraction mechanism. For example, the spring 88could be placed near and in contact with the spur gear or actuating gearin order to allow rotation in only one direction. It should beappreciated to those skilled in the art that still other ways ofrestricting movement of the gear rack and outer restraining member couldbe implemented without departing from the spirit and the scope of thepresent invention.

The delivery system of the present invention also includes a flushingsystem used to evacuate air from the system. It is important to evacuateair from the system when the delivery system is being used in apatient's vasculature since air bubbles can sometimes cause damage tovital organs. In other instances, it may be desirable to have a fluidpre-placed into the system to prevent the possible accumulation of bloodbetween the outer restraining member and the inner catheter member sincestagnated blood has the tendency to coagulate and cause thrombosis. Analternative flushing fluid besides saline could be an anti-clottingagent which can be placed in the annular space formed between the outerrestraining member and the inner catheter member to minimize bloodclotting. Such an anti-clotting agent includes heparin, which not onlyprovides an anti-clotting factor, but also includes smooth deploymentand reduces deployment forces. Additionally, if blood clots in theannular space, it would lead to higher deployment forces,non-deployments, and potentially partial deployments. An anti-clottingagent, such as heparin, also can be placed in the annular space formedbetween the outer sheath and the outer restraining member to preventclotting of blood within this space as well. It should be appreciatedother anti-clotting agents besides heparin could be utilized in the samefashion. For these reasons, it may be beneficial to pre-flush the systembefore placing the delivery catheter in the patient.

Referring now to FIG. 2, the flushing system consists of an opening 92or several openings extending through the inner catheter member 22 inthe area of where the distal portion 58 meets the mid-portion 56 of theouter restraining member 26. The openings are drilled through to theguide wire lumen 50 to effectively open up a passageway from the guidewire lumen to the annular space formed between the inner catheter member22 and the outer restraining member 26. A syringe can be attached to theluer fitting 52 on the catheter handle 12 and sterile fluid can bepumped into the guide wire lumen 50 in order to flush air from thesystem. A mandrel (not shown) can be placed in the guide wire lumen atthe tip 48 to block the flow of the sterile fluid through the distaltip. The sterile fluid is thus forced to flow out of the small openings92 into the annular space formed between the inner catheter member andouter restraining member. The fluid eventually flows past the collapsedstent where the fluid and any air in the system will escape through thedistal opening of the outer restraining member 26. Once fluid isobserved dripping from the distal end of the outer restraining member26, the mandrel can be removed since air has been evacuated from thesystem. Since the gap sizes are so small between the various components,capillary force prevents air from infiltrating the delivery system oncethe evacuation has been completed.

The components of the control handle can be made from conventionalmaterials well-known in the medical manufacturing art. For example, thecontrol handle can be made from a plastic or plastic-like material suchas ABS plastic, as can the various other components including thelocking mechanism, gears and gear rack.

It is to be understood that even though numerous characteristics andadvantages of the present invention have been set forth in specificdescription, together with details of the structure and function of theinvention, the disclosure is illustrative only and changes may be madein detail, such as size, shape and arrangement of the various componentsof the present invention, without departing from the spirit and scope ofthe present invention. It would be appreciated to those skilled in theart that further modifications or improvement may additionally be madeto the delivery system disclosed herein without departing from the scopeof the invention. Accordingly, it is not intended that the invention belimited, except as by the appended claims.

1. A system for delivering and deploying a medical device within apatient, the system comprising: a delivery catheter including an innercatheter member having a region for mounting the medical device thereonand an outer restraining member co-axially disposed over inner cathetermember and the medical device, the outer restraining member beingadapted for axial movement with respect to said inner tubular member;and a control handle having a rotatable thumbwheel connected to aretraction mechanism, the inner catheter member having a proximal endattached to the control handle and the outer restraining member having aproximal end attached to the retraction mechanism, wherein rotation ofthe thumbwheel causes linear movement of the retraction mechanism toproximally retract the outer restraining member sheath to uncover themedical device while the inner catheter member remains stationary. 2.The delivery system of claim 1, wherein the inner catheter memberincludes a guide wire lumen extending from the proximal end of the innercatheter member to the distal end of the inner catheter member.
 3. Thedelivery system of claim 1, further including a lock mechanism forpreventing the retraction mechanism from moving proximally until themedical device is ready to be deployed.
 4. The delivery system of claim1, further including means for evacuating air from the deliverycatheter.
 5. The delivery system of claim 1, wherein the deliverycatheter further includes an outer sheath which extends co-axially overa portion of the outer restraining member and is attached to the controlhandle, the outer sheath being attachable to the entry point of thepatient to provide a conduit for the delivery catheter to prevent thedistal end of the inner catheter member from moving distally when theouter restraining member is being retracted via the control handle. 6.The delivery system of claim 5, wherein the outer sheath is removablyattached to the control handle.
 7. The delivery system of claim 5,wherein the proximal end of the outer sheath is attached to a strainrelief member which is removably attached to the control handle.
 8. Thedelivery system of claim 7, wherein the strain relief member has aproximal end which includes a channel formed therein and the controlhandle has a distal recess formed therein and a tab-like memberextending into the distal recess, the channel being adapted to receivethe tab-like member to allow the strain relief member to be threadinglyengaged with the control handle.
 9. The delivery system of claim 8,further including a projection extending into the channel formed on thestrain relief member which forms an abutting surface that prevents thetab-like member from moving past it until a rotational force is placedon the strain relief member.
 10. The delivery system of claim 1, whereinthe retraction mechanism includes a gear rack which is slideable withina channel formed in the control handle and a spur gear attached to thegears of the gear rack, the thumbwheel having an actuating gear attachedthereto which mates with the spur gear to cause the gear rack to movelinearly within the channel when the thumbwheel is rotated.
 11. Thedelivery system of claim 10, further including stop means for preventingunintentional movement of the gear rack.
 12. The delivery system ofclaim 11, further including means for allowing motion of the gear rackin only one direction within the channel.
 13. The delivery system ofclaim 12, wherein the means for allowing motion of the gear rack in onlyone direction is a spring having an edge which contacts the distalsurface of the gears forming the gear rack to prevent distal movement ofthe gear rack.
 14. The delivery system of claim 1, wherein the controlhandle further includes means for allowing motion of the outerrestraining member in only one direction.
 15. The delivery system ofclaim 1, further including an anti-clotting agent placed between theouter restraining member and the inner catheter member.
 16. The deliverysystem of claim 5, further including an anti-clotting agent placedbetween the outer restraining member and the outer sheath.
 17. Thedelivery system of claim 5, wherein the outer sheath has distal portionwhich has a smaller inner diameter than the proximal portion of thesheath.
 18. The delivery system of claim 1, wherein the medical deviceis a self-expanding medical device.